The Record Warmth of March 2012

March 2012 will be remembered for its record-breaking warmth, particularly across the Upper Midwest. Long stretches of record highs and record warm lows were set, a lot of them significantly (10 degrees or more), including all-time March records.

Record warmth was not only found in the Upper Mississippi River Valley, but across the entire Midwest. According to the Midwestern Regional Climate Center, "The average temperature for the nine-state Midwest region was 50.3 degrees Fahrenheit, which broke the previous record of 46.9 degrees set over 100 years ago in 1910. Each of the nine Midwest states also set statewide records for the warmest March. Statewide records go back to 1895, and the existing records were all from the early to mid-20th century.

Throughout the month, over 6,400 daily record temperatureswere set or tied (including both warmest minimum and maximum temperature), with over 650 of them also setting records for the warmest temperature for any day in March. A majority of the records were set during the middle of the month, from the 14th through the 24th of March, when hundreds of records fell each day.

March average temperatures ranged from 10 degrees above average in Kentucky to 17 degrees above average in northwest Iowa, southern Minnesota, and western Wisconsin. During the record-breaking period from March 14 to 24, temperature departures ranged from at least 13 degrees above average in southwest Missouri to just over 29 degrees above average in central Wisconsin and northern Michigan.

Why So Warm?

The culprit was an unseasonably warm pattern over the Upper Mississippi River Valley region that took hold on March 10th. Aiding in this stretch was the lack of snow cover along and south of Interstate 94. The warmth and humidity intensified over the weekend of the 17th and 18th, in response to a deepening low pressure system over Montana. A slow cool down then ensued as more clouds and occasional precipitation moved across the region, associated with the low pressure system's cold front. Toward the end of the month, a slight warm up into the 70s set some new records, but temperatures dropped back to normal readings for the last few days of the month.

All-Time Warmest March Across The Upper Mississippi River Valley

The long stretch of well above normal warmth from the 10th to the 22nd, where records were being set nearly every day, helped to propel the average temperature for the month of March to new records.

All-Time Warmest March

La Crosse, WI

Rochester, MN

Ave Temperature

50.4

49.1

Previous Record

47.1 (1878)

42.9 (1910)

Normal

34.5

32.4

La Crosse Municipal Airport had an average temperature of 50.4 degrees. This was 15.9 degrees above the 1981-2010 March normal of 34.5 degrees. This easily surpassed the previous record of 47.1 degrees in 1878. March of 2012 was even 2.6 degrees warmer than the 1981-2010 April average. Only 30 April's were warmer than this March(monthly records date back to 1873: 139 April's).

Rochester International Airport had an average temperature of 49.1 degrees. This was 16.7 degrees above the 1981-2010 March normal of 32.4 degrees. This smashed the previous record by over 6 degrees (42.9 degrees in 1910). March of 2012 was even 4.4 degrees warmer than the 1981-2010 April average. Only 13 April's were warmer than this March (monthly records date back to 1886: 96 April's).

In addition to the record warmth at both La Crosse and Rochester, March of 2012 was the warmest at the following cooperative observing sites:

* Missing 1 to 3 days of temperature data, so the monthly temperature average is preliminary.

Listing Of Daily Temperature Records Set During March 2012:

La Crosse

Rochester

High Temperature

High Temperature

Date

Record

Previous

Date

Record

Previous

March 11th

67

66 in 2006

March 11th

63

60 in 1990

March 14th

75

68 in 1990

March 13th

66

63 in 1990

March 15th

71

68 in 1995 & prev

March 14th

74

70 in 1910

March 16th

79

75 in 1930

March 15th

73

67 in 2003

March 17th

83

78 in 1894

March 16th

78

73 in 1930

March 18th

80

71 in 1903

March 17th

81

66 in 1930

March 20th

74

71 in1918

March 18th

80

60 in 1910 & prev

March 22nd

77

73 in 1994

March 19th

77

69 in 1910

March 27th

78

77 in 1910

La Crosse

Rochester

Warmest Low Temp

Warmest Low Temp

Date

Record

Previous

Date

Record

Previous

March 15th

44-tied

44 in 1898

March 14th

49

44 in 1973

March 17th

62*

51 in 1894

March 16th

48

43 in 1990

March 18th

59

48 in 1968

March 17th

58

45 in 1966

March 19th

62*

59 in 1921

March 18th

61

46 in 1968

March 20th

57

45 in 1918

March 19th

62*

38 in 1976

March 21st

57

46 in 1946 & prev

March 20th

58

42 in 1918

March 22nd

57

47 in 1910

March 21st

57

44 in 1946

March 23rd

58

49 in 1987

March 22nd

59

40 in 2000

March 24th

54-tied

54 in 1910

March 23rd

55

49 in 1920

March 24th

54

52 in 1945

* Warmest low on record for March

La Crosse Warmest Daily Ave Temperature

Rochester Warmest Daily Ave Temperature

New Record

Previous Record

New Record

Previous Record

54.5 on March 11th

53.5 in 1977

50.0 on March 11th

49.0 in 1977 & 1990

60.0 on March 14th

58.5 in 1990

61.5 on March 14th

52.0 in 1990

57.5 on March 15th

53.5 in 1927

57.0 on March 15th

51.0 in 2003

61.5 on March 16th

60.5 in 1930

63.0 on March 16th

58.0 in 1930

72.5 on March 17th

64.5 in 1894

69.5 on March 17th

54.5 in 1966

69.5 on March 18th

57.5 in 1903

70.5 on March 18th

49.5 in 1918 & 1968

68.5 on March 19th

67.5 in 1921

69.5 on March 19th

53.0 in 1918 & 1976

65.5 on March 20th

58.0 in 1918

63.5 on March 20th

56.5 in 1918

65.5 on March 21st

58.5 in 1938

61.5 on March 21st

57.0 in 1918

67.0 on March 22nd

57.5 in 1910

67.0 on March 22nd

57.0 in 1938

63.0 on March 23rd

57.0 in 1945

La Crosse Highest March Dew Point

Rochester Highest March Dew Point

New Record

Previous Record

New Record

Previous Record

61 on March 17th

61 on March 23, 1936

62 on March 16th

56 on March 25, 2007

62 on March 20th

61 on March 17, 2012

62 on March 17th - tied

62 on March 16, 2012

March 2012 Temperatures In La Crosse,WI & Rochester, MN:

La Crosse, WI
High and Low Temperatures

Rochester, MN
High and Low Temperatures

Other Interesting Climate Factoids:

La Crosse, WI

On March 20th at 1:53 a.m. CDT, the dew point at the La Crosse Municipal Airport climbed to 62 degrees. This breaks the previous record of 61 degrees set on March 17, 2012 and March 23, 1936 for the highest March dew point. Dew point records for La Crosse date back to 1933.

The 83 degree high temperature on March 17th was the earliest occurrence of an 83 degree day in a year. The high temperature was 1 degree shy of the all-time March temperature of 84 set on the 29th of 1986.

Between March 17th and March 20th, average temperature departures from normal were 30 or more degrees. March 17th saw the largest departure from normal, a whopping 38 degrees!

Between March 14th and 22nd, 70 degree or higher temperatures were observed (9 consecutive days). This broke the longest string of 70 degrees or higher temperatures in March. The previous record occurred between March 23rd and 29th of 1910.

Rochester, MN:

On March 16th at 11:54 a.m. CDT and March 17th from 10:54 a.m. through 12:54 p.m., the dew point at the Rochester International Airport climbed to 62 degrees. This surpassed the previous March record of 56 degrees set on March 25, 2007. Prior to this year, the earliest 60 degree dew point was April 24th in 1990. Dew point records for Rochester date back to 1948.

The 81 degree high temperature on March 17th was the earliest occurrence of an 80 degree day in a year. The previous record was March 24th of 1910. The high temperature was 1 degree shy of the all-time March temperature of 82 degrees, also set on the 24th in 1910.

Between March 17th and March 20th, average temperature departures from normal were 30 or more degrees. March 18th saw the largest departure from normal, a whopping 38 degrees!

Between March 14th and 19th, 70 degree or higher temperatures were observed for 6 consecutive days. This is the second longest string of 70 degrees or higher temperatures in March. The record is 7 days between March 24 and 30th of 1910.

Mississippi River:

Water temperatures responded dramatically to the unprecedented warmth as well. At La Crescent Dam 7, the water temperature rose from 36 degrees at 7 a.m. on March 10th to 50 degrees at 7 a.m. on the March 20th. The water temperature topped out at 52 degrees on March 26th.

Mississippi Water Temperatures
at La Crescent, MN during Match 2012

Phenology:

Phenology is the study of periodic plant and animal life cycle events and how these are influenced by seasonal and interannual variations in climate.

The record warmth resulted in the growing season starting well ahead of normal. Soil temperatures quickly climbed from 31 degrees on March 9th to 58 degrees on March 18th. They topped out at 59 degrees on March 22nd. As clouds and precipitation moved into the area during the last week, they cooled off into the mid and upper 40s.

NWS La Crosse 2" Soil Temperatures for March 2012

In addition, the accumulated growing degree days climbed rapidly during the month. Areas along and north of the Interstate 94 corridor saw anywhere from 100 to 150. Meanwhile the remainder of the area accumulated between 150 and 210. Normally, we do not start accumulating growing degree days until after April 1st. The image below illustrates how the growing degree days quickly accumulated from March 13th through March 27th.

With the unusually warm soils and well above normal growing degree days, the growing season is well ahead of schedule. Forsythia bushes and spring flowers (crocuses, hyacinths, and tulips) were flowering anywhere from two weeks to a month ahead of schedule. Meanwhile fruit trees and rose bushes were at least a month to 6 weeks ahead of schedule. There were even some mushrooms at the end of March (usually not seen until May). The pictures below are from West Salem, WI.